The East London Line is shut for the whole of the Christmas week, while the start of a £320m upgrade is carried out.

Platforms on the Overground line from Highbury & Islington to New Cross/Crystal Palace/West Croydon/Clapham Junction – which passes through Dalston, Haggerston, Hoxton and Shoreditch – are going will be lengthened to cope with the line’s passenger demand.

The longer platforms will accommodate longer trains, which are being increased from four to five carriages.

The line opened just two years ago, but a spokesman for TfL said funding wasn’t in place at that time for this work.

He said: “Demand is now higher than it’s ever been, we didn’t have the money for this five years ago, but now we do have the money.

“We are limited about when we get funding from government, and how much.

“The money and effort that’s been thrown at this line means it is the best in Britain,” he added.

Since TfL took over the part of the network in 2007, London Overground has become one of the UK’s most reliable rail services and passenger numbers have quadrupled - from 2.5m in a typical four week period in 2008, to 11.2m now.

Putting on more trains to cope with the increased demand is not possible because of time tabling on parts of the line which are shared with other operators according to the spokesman.

The closure from Monday until Friday will enable work to take place at Canonbury, Highbury and Islington and Surrey Quays, and the line will be shut again later in the year while work is carried out at other stations.